Accuracy of Alcohol Thermometers Vs. Outdoor Spring Loaded Thermometers
Many homeowners have outdoor thermometers mounted on their houses so they can see what the temperature is outside. Some people are more concerned with the readability of the thermometers, while others are more adamant that the thermometer be accurate. Two of the more popular types of thermometer are the alcohol and the spring-loaded thermometer. While each type has its own benefits, they both look and work differently--yet which type is more accurate? Does this Spark an idea?
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History
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Spring-Loaded Thermometer Some researchers hold that Galileo first invented the thermometer in 1593, but the basic ideas of air expansion with heat and contraction with cold were known since 300 B.C. Italian Santorio Santorio is said to have been the first man to put a number scale on a thermometer, but no one knows how accurate that was. In 1714, Gabriel Fahrenheit invented the first reliable mercury thermometer.
Features
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The alcohol thermometer consists of a glass bulb attached to a long glass capillary tube. The bulb is filled with dyed ethanol, although some manufacturers use liquids such as toluene or kerosene instead. The liquid is topped off with nitrogen and vapor of whatever liquid is used. The back of the capillary tube is often painted white or yellow to make it easier to read the black graduation marks on the front of the tube.
The spring-loaded thermometer consists of two long strips of different metals that are bonded together and rolled into a coil. (This coil that looks similar to a spring in a watch is what gives this type of thermometer its "spring-loaded" name.) A "hand" is attached to the coil and points to the temperature scale on the front of the thermometer.
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How It Works
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The alcohol thermometer works on the principle that as temperature rises, liquids expand. Therefore, as the temperature rises, the alcohol in the capillary tube rises in the tube.
The spring-loaded thermometer is based on the idea that various metals expand at different rates. The coil is made of a bimetallic strip, so the metals expand and contract at different rates. The coil is sensitive to tiny temperature changes, and as the coil contracts or expands (winds or unwinds), it moves the attached "hand."
Uses
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Alcohol thermometers are used in measurements between -70 and +78 degrees Centigrade. This makes them useful for measuring outdoor weather and body temperature. The ethanol-filled thermometers can also be used to make measurements in extreme cold.
Spring-loaded thermometers are useful for measuring outdoor weather as well as temperatures in refrigerators, furnaces and ovens. Mercury switches are often attached to the bimetallic coil to turn furnaces off and on.
Summary
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Properly calibrated alcohol and the spring-loaded thermometers are both accurate for measuring outdoor weather. However, in extreme temperatures, alcohol thermometers would be a better choice for lower temperatures while spring-loaded thermometers would be more useful in measuring high heat and controlling switches.
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References
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- Photo Credit Image by Flickr.com, courtesy of Olivier Image by Flickr.com, courtesy of Randy
